6 most important features in coffee testing equipment – and how they help you achieve fresher, more consistent coffee.
At Home Roast, you will find everything from DiFluid, CoffMeter, and RoastRite. Here are the essential features (with examples of models that excel in each).
The Agtron scale (typically 0–150, where higher numbers = lighter roast) measures reflection of near-infrared light and precisely quantifies color. It directly correlates with development stages: light (80–100+) gives fruit & acidity, medium (55–80) balanced sweetness, dark (<55) caramel & bitterness – but below ~45–50, origin character (terroir) is often lost.
Key benefits & science:
Green coffee ideally has 10–12% moisture (ICO: 8–12.5%, often 11% as the sweet spot). Too high (>12–13%) → mold & defects. Too low (<10%) → rapid surface roasting, raw core & grassy notes. During roasting, water conducts heat into the bean – this controls the Maillard reaction and development.
Key benefits & science:
Aw measures "free" water (vapor pressure ratio, 0–1). It predicts microbial growth better than moisture%: <0.60 = no mold/mycotoxins. Ideal for green coffee: 0.45–0.55 aw – below 0.45 enzyme activity and flavor complexity are lost, above 0.55–0.60 the risk of oxidation and breakdown increases. High aw drastically shortens shelf life (e.g., cup-score drop within months).
Key benefits & science:
Density (g/L or bulk/true) indicates the bean's compactness – affects heat transfer. High density (hard beans, often high altitude/washed) requires more energy & longer time for even development. Low density (natural process) roasts faster → risk of scorching. It correlates with quality & roast profile.
Key benefits & science:
Particle size distribution (100–2500 µm) affects extraction: fine particles (<100–200 µm) cause over-extraction and bitterness but increase surface area and flavor. Bimodal distribution (typically from burr grinders) is normal – but uneven → channeling and uneven extraction. Optimal particle size distribution ensures balanced flow and maximum aroma without bitterness or sourness.
Key benefits & science:
After perfect roasting and grinding, TDS (Total Dissolved Solids) and extraction yield (EY) determine whether the taste hits the sweet spot. TDS shows the concentration in the cup (typically 1.2–1.5% for filter coffee, 8–12% for espresso), while EY indicates how much of the coffee’s mass has been extracted (SCA recommends 18–22%).
Too high EY (>22–24%) results in bitter, dry, and astringent coffee. Too low (<16–18%) leads to sour, thin, and incomplete flavour. With precise data, you can fine-tune grind size, water temperature, ratio, and brewing time – and see directly how your roasting performs in the final cup.
Key benefits:
With these features, you not only understand "what" is happening – but also "why" your roasting and cup improve. Start with one (for example, color or moisture) and build from there. Data makes roasting more enjoyable, precise, and skilled.
